Solvent extraction of oil



y 1952 .1. v. HUNN ET AL 2,605,271

SOLVENT EXTRACTION OF OIL Filed April 22. 1949 MISCELLA WASHER 3 HEAT EXCHA NGER .57 1 59 POLAR 55 l $512 5214;; L jz 35 .SEPARATOR 4/ t on.

1 RECOVERY 40 4z /3 v SOLVENT 30 OIL STORAGE A -/7 /5 l5 /6 /8 f L MIXER HEATER 5 EXTRACTOR /z k SEED 2 /9 MEAL. 20 7 1 47 COMPRESSOR 49 52/ 48 r\ i Z2 (Z3 1 05501. vawr- 7 43 -/ZER Z4 DISTILLAT/ON 46 COLUMN 44 I Z5 4? DE ooomzsk FATTY ACIDS AND 28 WA TER- INSOL UBLE I STEAM EXTRACTABLES 50 7 EXTRAC TED l MEI-l 1. WATER AND INVENTOR WA TER- SOLUBLE James V? Hunn EXTRHCTABLES Michael WPascaZ ATTORNEYS Patented July 29, 1952 UNITED 1 STATE SOLVENT EXTRACTION OF OIL James V. Hunn,

Avon Lake, and Michael W.

Pascal, Shaker Heights, Ohio, assignors to The Sherwin-Williams a corporation of Ohio Application April 22, 1949, Serial No. 88,952 1 (c1. zen-412.4)

16 Claims. 1

The present invention relates to a process for the solvent extraction'of vegetable oils from oilcontaining seeds, beans, nuts and the like more particularly to a processfor obtaining very high yields of vegetable oils from their natural sources, said oils being substantially entirely free of solid particles. The present invention also relates to a process for extracting oil from seeds, beans and nuts having a high oil content without the need for forepressing or special preparation.

-For the purpose of this description, the term seeds will be used throughout to denote not onlyseeds, but also beans, nuts, and other natural sources of vegetable oils such as cotton seed, castorbeans, soya beans, peanuts, fiaxseed, hemp seed, sunflower seed, oiticica, tungnut, coconut and the like. The solid particles which frequently accompany an extracted oil include those of colthose of slightly larger sizeloidal sizeas well as which are; derived from the cellular, cortical and/.orgproteinaceous constituents of theseeda:

andlthese particles will hereinafter be termed fines.--

-Vegetable'oils are generally recovered fromv their natural source by expression of the oil in expellers or other mechanical pressing devices such as the Icagepress or are recovered by treatment of. crushed seeds with a solvent for the oil. Occasionally combinations of these two methods havebeen used with advantage.

In the case of seeds containing a high oil content, such as flaxseed, it has been necessary to iorepress the seeds to remove about half of the available oil before solvent extraction in order to compress or harden the meal so that an excessive amount of fines are not produced. Such fines are extremely difficult to remove from the miscella. If in the forepressing operation too great a density of the meal is obtained, solvent extraction becomes difiicult and incomplete.

For solvent extraction of other seeds, such as soya beans, they must be conditioned and flaked on flaking rolls in order to extract the oil while obtaining a minimum amount of fines.

In all prior processes the prepared meal must be carefully handled to avoid comminuting the solid meal particles with consequent increase in the amount of fines.

A method for clarifying vegetable oils to remove the fines is described ,in our copending application Serial No. 64,142 filed December 8, 1948.

According to the present invention, an im-- proved method for the solvent extraction of and Company, Cleveland, Ohio,

vegetable oils from seeds has been devised in: which a combination of two substantially immiscible liquids are used. In general, theprocess involves the use of a non-polar solventfor the vegetable oil, and a polar liquid which preferena tially wets the solid material and fines'and is substantially immiscible with said oil solvent so that the extracted oil will be substantiallyentirely free of fines and other solid particles.

The phenomenon on which the, present inven-L tion is based is that the fines and other solid par-" ticles contained in a seed meal are hydrophilic' and are more easily wetted by polar liquids or aqueous polar solutions than by the solvents.

by the solvent for the oil when the seed me'alji'sj contacted with the solvent in theextractor. The oil contained in the seed meal, however, is sub-j stantially insoluble in the polar liquid binds:

readily dissolved by the solvent therefor; Thus the solvent preferentially dissolves the oil while the solid particles are preferentially wettedby the polar liquid. Since the polar liquidands'ole vent are substantially immiscible, a clean'flsepaeg ration is obtained with maximum extractionl'lpff the oil from the seed meal.

It is, therefore, an object of the present inveni tion to provide a process for obtaining clear, bril-' Another object of the presjent invention is to provide a unitaryprocess'by which vegetable oil may be substantially com',-' pletely recovered from its natural source; A still.

liant vegetable oils.

further object of the present invention is, the pro vision of a continuous process for extracting oilv from oil-containing vegetable materials; Addi tional advantages will become apparent from.

the following description of the invention.

In general any highly polar volatile liquidwhich has limited solubility in non-polar solvents, such as aliphatic hydrocarbons and.vegetable oils, or

which can be made essentiallyinsoluble in these. constituents by the addition of limited quantities of water, are usable in this invention.

The amount of Water that may be used the polar liquid is limited only by the solubility of Water in that particular liquid and the solubility of the water-soluble constituents of the seed meal in the polar liquid-water mixture. Forexe ample, certain seeds such, as fiaxseed contain mucilagenous constituents such as mucin. which will dissolve in the polar liquid when the water.

3 content thereof exceeds certain values, thus forming a thick, unmanageable mass. In the case of the lower alcohols, the water should not exceed about 60%. These limits are different, of course, for each polar liquid.

Polar liquids which have been found to be useful in the present method are low molecular weight aliphatic monohydric alcohols having not more than 4 carbon atoms, such as methyl, ethyl, propyl and isopropyl alcohol; water and alcohol solutions; aldehydes, such as furfural; organic acids; ethers; ketones, such as .aceton and methyl ethyl ketone; and the like.

In the case of the alcohols, which are preferred, it has been found that ethyl alcohol, propyl alcohol or isopropyl alcohol can be used satisfactorily. Methyl alcohol can also be used, but, due to its greater volatility and toxicity, it presents practical difficulties which render it less satisfactory than ethyl alcohol. Alcohols having a higher molecular weight than the propyl alcohols, such as butyl alcohol, may be used but are generally not suitable in the present process since they are not sufliciently volatile for easy removal from the extracted meal.

It has been found that aqueous solutions of ethyl alcohol and isopropyl alcohol are particularly suitable for use in the present process. However, when it is desired not to extract the fatty acids from the oil, it is generally necessary to-limit the concentration of the alcohol in water solution since the fatty acids are soluble in the more concentrated aqueous alcohol solutions. In the case of aqueous solutions of ethyl alcohol, isopropyl alcohol and the like, the concentration should not be greater than about 80% alcohol.

The oil solvent may be a saturated aliphatic hydrocarbon having from about 3 to about 9 carbonatoms and preferably 6 or 7 carbon atoms such as hexane, cyclohexane, heptane or their isomers. Commercial solvent containing substantial quantities of these materials may be used. The lighter hydrocarbons .such as propane, butane and pentane and their isomers may be. used but in this case it is generally necessary to'operate the system under pressure so as to maintain the solvent in a liquid phase. Heavier hydrocarbons can be used such as octane, but they require excessive temperatures for vaporization and azeotropic distillation as described hereinafter. Generally speaking the non-polar solvent must be substantially immiscible with the polar liquid and must be liquid under the conditions of operation which must, in turn, be such as not to affect the properties of the vegetable oil being extracted.

In, order to more clearly describe the invention, reference will be made to the accompanying drawing which is a diagrammatic fiow sheet of the process.

Referring now to the drawing, oil-bearing seeds arefirst comminuted to relatively small particle size, thus forming a meal. The meal is introduced through line I I to a mixer l2 in which the meal is thoroughly mixed with polar liquid introduced through line [3 and line M. The polar liquid, for convenience, will be referred to hereinafter as alcohol.

The alcohol-meal mixture is then passed to the extractor [5. The extractor may be of any conventional type and may conveniently include a screw conveyor along the bottom thereof for moving the meal from the inlet end to the outlet end. The extractor is provided with a temperature gradient such that the meal outlet end is tractor l5 to outlet line It.

relatively cool, for example between about F. and about F., while the meal inlet end is maintained at a higher temperature, for example between about F. and about F. The meal and alcohol mixture may be raised to the desired temperature byemploying hotalcohol from line I3 as hereinafter described orgby applying heat to the mixer I2. Alternatively the meal and alcohol mixture may be heated in a heater IS.

The non-polar solvent or oil solvent, which is introduced into the extractor through line H is relatively cool and the temperature thereof is gradually increased as it passes through the ex- Conversely, the alcohol and meal are gradually cooled as they pass through the extractor [5 to outlet I9.

As the meal is progressively moved through the extractor, it is thoroughly mixed with the oil solvent in the central zone thereof, whereby the solvent extracts the vegetable oil from the seed meal to form an oil-solvent solution or miscella. The miscella is withdrawn from the extractor through line H! for further treatment as described below.

The oil-free meal and the alcohol are withdrawn from the extractor l5 and passed to a compressor 26 in which the meal is compacted to express as much of the alcohol as possible. The expressed alcohol is withdrawn through line 2| and the meal is passed from the compressor 20 through line 22 to a desolventizer 23. Al-- though the mixer 12, heater l6, extractor l5 and compressor 20 have been described as separate pieces of apparatus, it will be understood that a single piece of apparatus adapted to-carry out these functions can be used.

The recovered alcohol, if substantially free of fatty acids or other alcohol extractable materials contained in the oil, may be passed from line 2! to line l4 and to the mixer [2 for admixture with fresh meal. The extracted meal which still contains substantial quantities of alcohol is treated in the desolventizer 23 for removal of substantially all of the remaining alcohol; For purposes to be described later, some of the nonpolar solvent can be introduced into the desolventizer 23 through line 24. The desolventized' meal is then passed through line 25 to a deodorizer 26 for the removal of traces of alcohol and/or solvent from the meal. To assist the deodorization, steam or other suitable material may be admitted through line 21 to the deodorizer 26. The extracted meal is then withdrawn from the system through line 28.

The miscella which is withdrawn through line l8 from the extractor I5 is normally passed through line 29 into the bottom of a miscella washer, or scrubber 3B and passes upwardly therethrough while alcohol which is introduced through line 3| into the top of the scrubber: 30 passes downwardly therethrough, thereby removing from the miscella any fines or other solid particles which may have been carried therewith from the extractor; This particular step of the present process is described more fully in our above-mentioned application Serial No. 64,142..

An additional function of the scrubber 30 is to preheat the alcohol which is then withdrawn from the bottom ofscrubber 30 through line I3 for introduction into the mixer I2. The miscella is then withdrawn from the top of the scrubber 30 through line 32 and is passed to an oil recovery system 33 in which the solvent, such as hexane or heptane, is removed from the oil,

for example by distillation; The recovered oil is then withdrawn from the system through line 34. The recovered solvent will contain'aasmall amount of dissolved alcohol which ,has been picked up in the extractor I5 and/onscrubber 30. This is due to the fact that alcohol is slightly more soluble in the miscellathaninthe oilfree solvent, theoil actingin the nature of a mutual solvent for the non-polar solvent and; alcohol. The recovered solvent is passed through line,; 35 to an alcohol;-solvent separator 36. To obtain as high a degree of separation as possible,--it may bedesirable to cool the recovered solvent when introducing it into separator 36. The substantially solvent-free alcohol is passed through line 31 to astorage tank38 and the substantially alcohol-free solvent is passed through line 39 to storagetank 40.

When extracting oil from certain seeds or beans in which little or no fines are found, it may be desirable to pass the miscella directly fromextractor i5 through line 3 to'line 32 and the oil recovery'system 33, thus by-passi'ng the scrubber'. '30. 'In this event it willilikewise be desirabletov pass the alcohol from storage tank through lines 4| and '42 to line l3, thus bypassing the scrubber 30.,

The .vapors "recovered from .desolventizer 23 and deodorizer 25 are withdrawn, respectively, through lines 43 and 44'. If these vaporscontain' no substantial amounts'of the solvent, they maybe passed directlyz t'oz line l4 together'vvith the alcohol fromline 2| but since solvent may be present as described below, they are preferably passed through line 45 to a'distillation colum'n46."

When they vegetablematerial being treated contains substantial amounts of fatty" acids and/or" unsaponii'iable materials, they will be largely dissolved inithe alcohol which is expressed from theextrac'ted meal incompressor 201- If'this alcohol were continuously recycled directly to the mixer |2 through line l4 there would be a build-up in 'thesystem' ofthe fatty acids and unsaponifiable materials. This would be highly undesirable since the fatty acids act as a mutual solventfor the alcohol'and solvent,

,to form the miscella.

extractable materials can be withdrawn andsub gsequently allowed to, settle or can be allowedto stratify in thebottom of the still andbe withdrawn ,through' lines 50; and El, respectively. The lower layer comprises water andthose materials which are water and alcohol-solublewhile the upper layer comprises fatty acids and those materials which are alcohol-soluble but waterinsoluble. g

In general the main, cycle for the solvent is from tank 40, through line H tothe extractor |5 whereit extracts the oil from the seed meal The miscella is then passed through. lines I8 and 29 to scrubber 30. where any fines which may have been carried. along therewith are removed. The miscella then-passes through line 32 to an oil recovery system 33. from which the oil is withdrawn through line 34 and the solvent, together with small amountsof alcohol, are passed through line 35 to the separator 35. From the separator 36 the solvent is returned to storage tank through line 39..

The alcohol cycle is from storage tank. 38

' through lines 4| and 3| to the scrubber 30 where it picks up any fines contained in the miscella and is preheated before-being passedthrough thereby tending to prevent the desired phase separation in the extractor t5." It is, therefore,

proposed to intermittently or preferably continuously pass'the alcohol in line '21 to line 45 and thence into the distillation column 46 in order to remove these alcohol-soluble materials from the system: a

The distillation column '46 or any other suitable equipment is operated with a temperature gradient so as to effect a separation between an alcohol-solvent azeotrope and alcohol. The temperature at the top of thecolumn is regulated in'accordance'with the boiling point of the azeotrope. The azeotropic vaporsare passed through lines 41 and 35 to separatorj36 for phase separation together with "the recovered solvent from oil recovery system 33-. At alowerpoint' in the still where a higher temperature is maintained, there is provided a draw-on" for excess alcohol. The alcohol so withdrawn'may be passed while hot through line- 43 toline M'and thence directly 'to the mixer l2 or it maybereturnedto the alcohol 'storage tank 38 throu'gh line 49. The inlet line-45 enters the column46 near the bottom thereof as .shown-inthedrawing. The still bottoms which'include' water from the mois.-.v

ture content of the seeds orfromsthe steamintroducedinto.thegdeoclorizerit; fatty acids and.

line l3 to the mixer |2 The alcohol then passes through the optional heater Hi, the extractor li to the compressor 21!. Most of thealcohol is removed from the extracted meal in compressor 20 and is normallypassed through lines 2| and 45 to the distillation column 46. A'portion of the alcohol may be returned directly to the mixer [2 through lines 48 and M while the remaining portion of the alcohol in the form of the alcohol-solvent azeotrope, passes through lines 4] and 35 to the separator 36. The alcohol iswithdrawn therefrom through'line31 and is returned to the. alcohol storage tank 38.

s It will, of course, be understood that the lower aliphatic alcohols are slightly soluble in the hydrocarbon solvent and that the hydrocarbonsolvent is slightly soluble in the alcohols; the degree of solubility in each case decreasing with temperature and water content.

One of the important featuresfof the present invention is the utilization of the phenomenon that the hydrocarbon solvents and the aliphatic alcohols which may be used in the present prophenomenon, it is possible to desolventize the extracted meal to a much greater degree than is possible by merely attempting to evaporate the liquid from the Wetted extracted meal. The alcohol-wet meal which is passed from the compressor 2D to the desolventizer 23 cannot be properly desolventized by the soleuse of heat since the temperatures necessary to evaporate substantially all of the alcohol would adversely affect the proteinaceous material containedjin the extracted meal. However, by adding aregulated quantity of the hydrocarbon solvent through line 24 to the desolventizer 23, itis possible to evaporate an azeotrope of the hydrocarbon solvent and the alcoholflat a lower temperature, thus preventing degradation and other adverse effects on the proteins. When the vapors in line substantially entirely comprise the desired azeotrope, they may be passed from line 43 through line 52 directly toline 41. However, if substantial quantities of excess alcoholor solvent are present in these vapors, theyare preferably passed linef45.

to the column 46- through through line-l1 iscontrolled sci-that thespecific gravity-of the miscella will be less than the specific gravity of the polar liquid. This ensures a clean-separation of the miscella and the polar liquid in the extractor l5 and also assists in the operation of the scrubber 30." Normally an increase in the proportion of oil in the miscella, increases the specific gravity thereof. Therefore, the proportion of oil in the miscella must not exceed that which will result in a specific gravity greater than the specific gravity of the particular polar liquid being used. For example, when an 85% ethyl alcohol solution is used in:the extraction of linseed from fiaxseed with'h'eptane,

the miscella should not have an oil concentration greaterthan 40%.

The proportion of non-polar solvent to polar liquid is not critical-and 'may vary fromjust suflicient polar liquid to thoroughly wet the meal to much greater quantities that may be in excess of non-polar solvent.

We have: found that for eificient. operation, sufficient polar solvent should be used to form a fiowable slurry. with the meal. When these conditions exist, efiicient separation of the two phases readily takes place.

When aqueous solutions of polar wetting agents are used, the concentration of the wetting agent in the solution mustbe controlled to'satisfy, as nearly as possible; two factors. more important factor relates to: the solvent power of the polar liquid for the solvent or ,miscella, whereas the second factor relates to the interfacial tension of the polar liquid.

To meet the first-mentioned factor, the polar liquid'should be diluted with. sufficient water to decrease the solubility of the polar liquid in the miscella to an insignificant value while the secend-mentioned factor calls for dilution with a minimum quantity of water so as to obtain as low an interfacial tension as possible while .at the same time complying with the first factor. For example, if a highly concentrated aqueous solution of an alcohol and heptane were used, the oil acts in the nature of a mutual solvent for the heptane and the alcohol so that the alcohol solution might contain appreciable quantities'of the heptane and oil'." Occasionally it is necessary to add relatively-large quantities of water to the polar'liquid in order to reduce the solvent power of the aqueous polar liquid solution for oil to a negligible value,'thus raising the interfacial tension to a value which is higher than would be normally desired. Such solutions-may nevertheless be used inthe present invention proVid'ed the seed meal and polar solution are mixed with'su'fficient agitation and'for'sucha periodof time as to ensure wetting of all of the fines-and solids in the-meal. 7

Although the present invention has been described" with particular reference to the accom} panyingfiowfsheet, it will be understood that the present invention-may be carried out in various different ways-without departing from the spirit of the invention. Also, it will be urider-' stood-that wherever'a-specific type of apparatus has been described, other types of apparatus may be used'for performingthe same orfsimilar func The first and tions. 'For'simplicity:sakerepresentations of conventi'onal p d ppa Such Valves pumps; heat exchangers and the Iike 10 been included in the drawings sincethesewillbe readilyunderstood by those skilled in the art. This application is a continuation-in-part of our copendingapplication Serial Number 64,142

as to form a fiowable slurry with the meal, pass-- ingsaid slurry through an extraction zone, pass-- ingan aliphatic organic solvent for the oil through said zone counter-currently to the direction of said slurry'and in admixture therewith; said aqueous solution containing sufficient water to render said'solution substantially immiscible with the aliphatic solvent and insumcient water tocause complete insolubilityof the oil in-the aqueous solution, agitating the mixture in said extraction zone whereby the oil in said meal is taken up by said aliphatic solvent to form a miscellawhile said substantially oil free; meal remains in said, slurry with said aqueous solution, progressively separating the mixture into two phases, one being the miscella and the other the substantially oil-free slurr and separately withdrawing the miscella and said substantially oil-free slurry from said extraction zone.

2. A method as claimed in claim 1 and further comprising recovering said aqueous solution from said substantially oil-free slurry, washing said miscella with at least'a portion of said recovered aqueous solution to remove any residual meal therefrom and recovering said aliphatic solvent from said washed miscella.

3. A method of extracting oil as'claimedin claim 1 and further comprising recovering said aliphatic solvent from said miscella adding at least a portion of said recovered aliphatic solvent to said substantially oil-free slurry to' form a mixture. therewith, heating said mixture to evaporate said aliphatic solvent and said aqueous solution asan azeo'tropic mixture from said meal and separating the aliphatic solvent from the aqueous solution in the azeotropic mixture.

4. A method of extracting oil from oil bearing seeds comprising mixing a meal of crushed oil bearing. seeds with an aqueous solution .of hydrophilic. organic solvent for. oil. in such amount: as to form afiowable slurry with the .meal, mix; ing said slurry with analiphatic hydrocarbon solvent for oil in an extraction zone, said aqueous phases, one being the miscella and. the other aslurry of substantially oil free meal and the aqueous, solution, and separately withdrawing said phases from said extraction zone.

'5. lfl'method of. extracting oil from oil bearing,

seeds comprisin mixing, in an extraction zone;

agmeal of crushed oil bearing seeds with a:suf.-i fic ent amo of an aqueous solution. of a h d ophilicorganic solvent for oil to form a flowable slurry and with an aliphatic hydrocarbon solvent for. oil, for extraction of theofl from said meal, said aqueous solution containing sufficientwater to' render said solution substantially im-J miscible with the aliphatic hydrocarbon solvent:

but insufficient water to cause complete insolubility of the oil in the aqueous solution, agitating the mixture in said extraction zone, progressively separating one phase comprising a relatively clear miscella from a second phase comprising substantially the aqueous solution and the oil-free meal and separately withdrawing said phases from said extraction zone.

6. A method of extracting oil as claimed in claim 5 wherein the hydrophillic organic solvent for oil is selected from the group consisting of low molecular weight aliphatic monohydric alcohols, aldehydes, organic acids, ethers and ketones.

7. A method as claimed in claim 5 wherein the aqueous solution recovered from said extracted meal is treated for the removal of those materials originally contained in the meal which are soluble in said aqueous solution.

8. A method as claimed in claim 5 wherein the hydrophilic solvent comprises an alcohol.

9. A method as claimed in claim 8 wherein the concentration of the alcohol in the aqueous solution is not greater than about 80%.

10. A method as claimed in claim 9 wherein the concentration of the alcohol in the aqueous solution is from about 40% to about 80%.

11. A method as claimed in claim 8 wherein the alcohol is a low molecular weight aliphatic alcohol.

12. A method as claimed in claim 11 wherein the alcohol is isopropyl alcohol.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,917,734 Rewald July 11, 1933 2,200,390 Freeman May 14, 1940 2,228,040 Voogt Jan. '7, 1941 2,384,388 Monte et a1 Sept. 4, 1945 2,480,221 Caplan Aug. 30, 1949 2,484,831 Hutchins et al Oct. 18, 1949 2,489,599 Trottmann Nov. 29, 1949 OTHER REFERENCES Meyer, High Polymers, Vol. IV, page 576. Ind. & Eng. Chem. 38, 1946, page 642. 

1. A METHOD OF EXTRACTING OIL FROM OIL BEARING SEEDS COMPRISING CONTACTING A MEAL OF CRUSHED OIL BEARING SEEDS WITH AN AQUEOUS SOLUTION OF A HYDROPHILIC ORGANIC SOLVENT FOR OIL IN SUCH AMOUNT AS TO FORM A FLOWABLE SLURRY WITH THE MEAL, PASSING SAID SLURRY THROUGH AN EXTRACTION ZONE, PASSING AN ALIPHATIC ORGANIC SOLVENT FOR THE OIL THROUGH SAID ZONE COUNTER-CURRENTLY TO THE DIRECTION OF SAID SLURRY AND IN ADMIXTURE THEREWITH, SAID AQUEOUS SOLUTION CONTAINING SUFFICIENT WATER TO RENDER SAID SOLUTION SUBSTANTIALLY IMMISCIBLE WITH THE ALIPHATIC SOLVENT AND INSUFFICIENT WATER TO CAUSE COMPLETE INSOLUBILITY OF THE OIL IN THE AQUEOUS SOLUTION, AGITATING THE MIXTURE IN SAID EXTRACTION ZONE WHEREBY THE OIL IN SAID MEAL IS TAKEN UP BY SAID ALIPHATIC SOLVENT TO FORM A MISCELLA WHILE SAID SUBSTANTIALLY OIL FREE MEAL REMAINS IN SAID SLURRY WITH SAID AQUEOUS SOLUTION, PROGRESSIVELY SEPARATING THE MIXTURE INTO TWO PHASES, ONE BEING THE MISCELLA AND THE OTHER THE SUBSTANTIALLY OIL-FREE SLURRY, AND SEPARATELY WITHDRAWING THE MISCELLA AND SAID SUBSTANTIALLY OIL-FREE SLURRY FROM SAID EXTRACTION ZONE. 